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The Garden Plot for December 07, 2007
3:55 PM - 4:00 PM
[Program Website]
Today's Highlight: “Snow Damage”
All that snow, all at once in November, wreaked havoc with shrubs and trees in Western Montana. The heavy snow caused branches and whole plants to bend, droop, split, and break. Now is a good time to assess plants for “snow-load” injury. Look first for bark splitting and tearing, as well as limb and branch breakage. Then, look for other species-specific concerns:
Injured Conifers can become targets for disease infections and insect infestations next spring. Bark beetles, such as pine engravers, are attracted to broken tree tops and branches on the ground. If this debris is not removed by early spring, beetle populations may build and move into adjacent healthy trees.
Wounded shade trees are more susceptible to stem-boring insects, particularly poplar, aspen, willow, and birch trees. Stem-boring insects can infest a tree and eventually kill it if left untreated.
Large trees can become a hazard if they are injured. An injured tree should be assessed by a professional for falling branch potential, splits in trunk and branch forks, and the risk of eventual entire tree collapse.
Even if winter-damaged trees are properly pruned, some discoloration from bacteria and fungi may occur, but little decay will develop. You should probably hire a professional arborist to prune large trees. For smaller trees and shrubs, prune out damaged branches, using the following 3-cut method:
1) Cut part way through the underside of the branch, two to six inches from the trunk.
2) Cut the branch top, just past the first cut and remove the branch;
3) Remove the remaining stub close to the trunk, but just past the branch collar. The branch collar is the raised area where the branch meets the trunk or main stem.
Torn bark may need to be repaired. Remove the bark back to where it is attached to the tree. Use a sharp knife to smooth the ragged edges. Try not to expose the green (cambium) tissue, which is just under the bark. Keep wounds as narrow as possible since the wider the wound, the slower it heals.
While immediate plant injury, such as broken branches, can be taken care of now, you will probably have to re-assess plant damage when growth begins in the spring. The best time to shape and prune bending, drooping trees and shrubs is when buds are ready to break next spring.
Shrubs require shaping and thinning as injured branches are removed. Remove injured branches back to the ground, or to the main stem, if they are badly broken or bent. A branch is too far bent if it will not stand up on its own once the weight of the snow is removed. Drooping branches can sometimes be saved without pruning. Gently pull the branches back into position and tie them to the central stem. This balances small trees and shrubs until the branches become strong. Another trick for bending shrubs is to pull the branches back into position and prune them just at the point where the branch starts to bend. Always prune 1/8 to ¼ inch above an outward-growing bud when shaping shrubs; it helps keep shrub centers open, allows aeration, and thus prevents disease.
For more information on how to care for snow-injured trees, contact your local county extension agent.
Helen Atthowe's new short program of gardening tips
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